Taking on the indigo challenge.
Blue denim goes green

Case study

How our experienced team solved a complex dyeing conundrum.

Design, synthesis and scale-up of a novel molecule with significant improvements in the production process of dyed textiles for VF Jeanswear LP


The Challenge

Indigo is a difficult compound to work with due to its poor solubility in most solvents and its low affinity for cotton. It requires a complex and time-consuming dyeing process which uses large amounts of water and produces waste products that cannot be cheaply recycled. AF ChemPharm was awarded the project to find solutions to the technical challenges of working with indigo which led to a substantial international patent with AF Chempharm’s scientists as co-inventors.

We set out to improve the dyeing process by finding an indigo derivative that:
• is stable and water-soluble
• is easily synthesised
• converts back to indigo through a mild chemical process
• eliminates the need for auxiliary chemicals in the dyeing process
• reduces the dyeing time
• reduces the amount of water used
• reduces the need for an oxygen-free atmosphere
• is more environmentally friendly
• makes the dyeing process more cost-effective

Our Approach

The proposal

AF ChemPharm answered a global call, by Innovia Technology, for proposals to address the technical challenges of working with indigo on behalf of VF Corporation (VFC).
We proposed to modify (derivatise) the indigo to a stable water-soluble moiety which would then, after deposition on to cotton rope, decompose back to indigo by a mild chemical process.

After several meetings with Innovia and VFC, AF ChemPharm was awarded the project.

Research

Over a period of 4 years, we worked closely with our new partners to research and synthesise an extensive array of indigo derivatives, targeting the two active centres within the indigo molecule, the carbonyl and the nitrogen centres.

Compound screening

We screened the compounds for their ease of synthesis, solubility in water, facile decomposition and cost-effectiveness. Finally, we selected a range of nicotinoyl compounds. Following their synthesis, isolation and characterisation, these compounds were sent to our partners’ process laboratory in the US for trial experiments on yarn. They were tested for the depth of colour, dyeing time (number and duration of dips), durability of the dyed yarn and various other factors.

Lead identification

Four compounds were selected for their ease of synthesis and outstanding performance, but one compound, in particular, exceeded all expectations. Indeed, the desired strength of colour was achieved with only one dip with almost no waste indigo precipitating out in the bath; this not only presents a considerable economic advantage but hugely significant environmental benefits for the textiles industry.

Lead optimisation, development and scaling up

Following the lead compound selection, the next task was to optimise and scale-up synthesis. A period of intense development work followed during which AF ChemPharm worked in close collaboration with a reputable German manufacturer to ensure the smooth transfer of technology from laboratory to plant within a quality system. A highly skilled and experienced team handled the documentation for all aspects of development, production and quality control.

The final compound

The compound with best performance was taken forward for manufacturing on a pilot plant scale, transforming our R&D concepts into commercially viable processes

This collaboration has resulted in one substantial world patent and also a second patent has been filed (WO2017223369A1), with AF ChemPharm scientists as co-inventors.

The Results

Taking on a chemistry challenge that others would have shelved long ago requires a collaborative working relationship; a partnership between like-minded scientists.

We set out to improve the indigo dyeing process and developed a modified indigo compound that provides a number of benefits over the conventional use of leuco-indigo. Together we have achieved both. The new compound:

• is stable in the presence of oxygen and has improved water solubility compared to leuco-indigo
• can remain in aqueous solution for a commercially significant length of time
• is easily synthesised
• converts back to indigo through a mild chemical process
• removes the need for an oxygen-free atmosphere
• eliminates the need for reducing agents and strong alkalis in the dyeing process
• minimises the duration and number of dips, thus reducing the dyeing time
• is more environmentally friendly
• foam dying process can now be applied under atmospheric conditions which reduces water usage by 95%
• makes the dyeing process more cost-effective


AF ChemPharm’s proposal to modify the indigo to a stable water soluble moiety (bottom of the three chemical structures shown) that reduced cost, increased throughput and improved sustainability of the denim-dyeing process. The new compound developed by AF-ChemPharm could be used in existing plants in place of current methods with little or no change to production equipment.

AF ChemPharm’s proposal to modify the indigo to a stable water soluble moiety (left of the three chemical structures shown) that reduced cost, increased throughput and improved sustainability of the denim-dyeing process. The new compound developed by AF-ChemPharm could be used in existing plants in place of current methods with little or no change to production equipment.


Overall the new indigo derivative reduces cost, increases throughput and improves the sustainability of the denim-dyeing process.

“We have partnered with AF ChemPharm over 2 years to design, synthesize, and scale-up a novel compound. Their expertise and professionalism has enabled us to produce the compound in ton quantities for use in our plants worldwide.”

Project Coordinator, Apparel manufacturer

Contact the team at AF ChemPharm and let us solve your chemistry challenges.

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